Along with the spread of a composite resin as a dental restoration material, strong adhesion which is easily operated, safe and reliable is required between a tooth and the composite resin. As one of conventionally used bonding methods is a typical method of bonding a restoration material in which a series of operations such as the etching of a tooth with an acid such as phosphoric acid or citric acid, rinsing in water, drying, primer treatment, drying, the application of an adhesive, polymerization and the filling of a composite resin are carried out sequentially. The bonding step in this method is complicated and takes time in the actual clinical treatment, and stable and reliable adhesion is not obtained yet.
Then, a bonding method for simplifying this complicated step is now under study. JP-A 3-240712 and JP-A 7-82115 propose a primer which eliminates an etching step. In this proposal, a tooth is treated with a self-etching primer which is said to enable etching and primer treatment to be carried out at the same time and dried, and then an adhesive is applied to the tooth. That is, the surface of the tooth having a cavity is treated with the self-etching primer to infiltrate the self-etching primer into the tooth while it melts a smear layer produced by the formation of the cavity. Then, by applying a bonding agent to the tooth, the self-etching primer and the bonding agent are cured together to obtain a strong adhesive layer.
However, currently commercially available self-etching primers of this type require a polymerization catalyst and a polymerization accelerator for curing a polymerizable component contained in the self-etching primer, and it is necessary to separate the polymerization catalyst from the polymerization accelerator in order to obtain a self-etching primer having high storage properties and stabilized adhesion performance. Therefore, currently commercially available self-etching primers are each composed of two liquid self-etching primers, i.e., one containing a polymerization catalyst and one containing a polymerization accelerator, and the two liquids must be mixed together before use. Therefore, it is hard to say that they are easy to operate, and unstable adhesion may occur due to a metering error. JP-A 6-40838 also fails to suggest the long-term storage stability of a mixed composition comprising a polymerizable component and a polymerization accelerator.